The present disclosure relates to sheet processing devices that perform preset processing on a sheet, such as stapling, and image forming apparatuses including such a device.
Image forming apparatuses of some type include a post sheet processing device. The post sheet processing device performs post processing, such as stapling, on a sheet on which an image is formed by an image forming apparatus main body, such as a copier, a multifunction peripheral, etc.
Some post sheet processing device includes an exit tray and a staple contact strip. To the exit tray, book-like bound sheets, that is, a plurality of sheets subjected to stapling are ejected. The staple contact strip is provided at a position corresponding to a staple part of sheets subjected to stapling and is capable of intercepting a light beam of a photointerrupter.
In view of the fact that where the book-like bound sheets are stapled at their one corner part, the staple part is higher than any other part and the inclination of the topmost surface of the book-like bound sheets becomes large, the post sheet processing device detects the upper limit of the book-like bound sheets stacked on the exit tray and moves the exit tray downward. In other words, when the staple contact strip comes in contact with and is pushed upward by the topmost surface of the book-like bound sheets ejected to the exit tray, the light beam of the photointerrupter is intercepted, so that the upper limit of the book-like bound sheets stacked on the exit tray is detected. Accordingly, the exit tray is lifted down so as to allow the next book-like bound sheets to be ejected.